Acetic acid production process
View Patent ↗A method for determining the characteristic of one or more components in a step of an acetic acid production process using Raman spectroscopy. The process includes providing a feed stream comprising multiple components to a separations unit, one of the components being acetic acid, the separations unit separating the feed stream into two or more exit streams having a different composition from one another, and measuring a characteristic of one or more of the components by Raman spectroscopic analysis.
1. A method for measuring a component of a separations unit downstream from the acetic acid reactor comprising:
(i) directing a feed stream to a separations unit, wherein the feed stream comprises the following components:
methyl iodide,
water,
methanol,
methyl acetate,
acetaldehyde,
acetic acid,
alkanes and
propionic acid,
(ii) separating the feed stream in the separating unit into an overhead exit stream and a bottoms exit stream
wherein the overhead exit stream comprises the following components:
30 wt. % to about 70 wt. % methyl iodide,
10 wt. % to about 40 wt. % water,
5 wt. % to about 15 wt. % methyl acetate,
less than 2 wt. % acetaldehyde,
5 wt. % to about 35 wt. % acetic acid,
1 wt. % to about 10 wt. % alkanes and
wherein the bottoms exit stream comprises the following components:
80 wt. % to 100 wt. % acetic acid,
3 wt. % to about 20 wt. % water; and
measuring a characteristic of one or more said components in said separations unit by Raman spectroscopic analysis.
2. The method of claim 1 , wherein the characteristic measured is concentration or density.
3. The method of claim 1 , wherein the separations unit is a distillation column or a decanter.
4. The method of claim 3 , wherein the characteristic of one or more components in a light phase of the decanter is measured.
5. The method of claim 3 , wherein the characteristic of one or more components in the distillation column bottoms is measured.
6. A method for controlling an acetic acid production process, comprising:
(i) reacting methanol and carbon monoxide in the presence of a carbonylation catalyst to produce a reactor product comprising acetic acid;
(ii) separating the reactor product in a separating unit into an overhead exit stream and a bottoms exit stream
wherein the overhead exit stream comprises the following components:
30 wt. % to about 70 wt. % methyl iodide,
10 wt. % to about 40 wt. % water,
5 wt. % to about 15 wt. % methyl acetate,
less than 2 wt. % acetaldehyde,
5 wt. % to about 35 wt. % acetic acid,
1 wt. % to about 10 wt. % alkanes and
wherein the bottoms exit stream comprises the following components:
80 wt. % to 100 wt. % acetic acid,
3 wt. % to about 20 wt. % water;
(iii) measuring the characteristic of one or more components in a separations unit downstream from said reactor by Raman spectroscopic analysis; and
(iv) adjusting the conditions in a reactor or in any subsequent step of the acetic acid production process.
7. The method of claim 6 , wherein the separations unit is a distillation column or a decanter.
8. The method of claim 6 , wherein the characteristic of one or more components in a light phase of the decanter is measured.
9. The method of claim 6 , wherein the characteristic of one or more components in the distillation column bottoms is measured.
10. The method of claim 6 , wherein said adjusting the conditions comprises modifying the temperature or flow rate of a feed, recycle or exit stream of a reactor or separations unit or modifying the temperature of a reactor or separations unit.
11. The method of claim 6 , wherein the catalyst is a rhodium catalyst.
12. The method of claim 6 , wherein the reaction occurs in the presence of a catalyst stabilizer selected from the group consisting of pentavalent Group VA oxides, metal iodide salts, and mixtures thereof.
13. The method of claim 9 , wherein the catalyst stabilizer is a phosphine oxide.